Atom
Atom ({not transcribed}) , noun
[Latin atomus, Greek {not transcribed}, uncut, indivisible; 'a priv. + {not transcribed}, verbal adj. of {not transcribed} to cut: compare French atome. See Tome.]
1.
(a) (Physics) An ultimate indivisible particle of matter.
(b)
(Physics) An ultimate particle of matter not necessarily indivisible; a molecule.
(c)
(Physics) A constituent particle of matter, or a molecule supposed to be made up of subordinate particles.
These three definitions correspond to different views of the nature of the ultimate particles of matter. In the case of the last two, the particles are more correctly called molecules.
2.
(Chemistry) The smallest particle of matter that can enter into combination; one of the elementary constituents of a molecule.
3.
Anything extremely small; a particle; a whit.
There was not an atom of water.
Atom , transitive verb
To reduce to atoms. [Obsolete] — Feltham